Chemo drugs often cause liver inflammation, making it necessary to lower the dose or suspend treatment until the inflammation subsides. These interruptions in therapy can make treatment less effective, the researchers said.

"We found that milk thistle, compared to placebo, was more effective in reducing inflammation," said lead researcher Dr. Kara Kelly, from New York-Presbyterian Hospital/Columbia University Medical Center's Herbert Irving Comprehensive Cancer Center in New York City.

"If these results are confirmed, milk thistle may allow us to treat liver inflammation or prevent it from occurring, which will allow better delivery of chemotherapy drugs," she added.

The report is published in the online edition of Cancer.

Milk thistle, a longtime folk remedy, is often recommended to treat liver damage and mushroom poisoning. No other treatment for liver toxicity exists, Kelly said.

For the study, Kelly's team randomly assigned 50 children undergoing chemotherapy for acute lymphoblastic leukemia to receive milk thistle or a placebo for 28 days. All the children had liver inflammation at the start of the study.

Twenty-eight days later, the children who had received milk thistle had improved liver enzymes, compared with the children who received a placebo, the researchers said.

The milk thistle group had significantly lower levels of one enzyme in particular, AST, and a trend towards lower levels of another enzyme called ALT, Kelly's group found.

In addition, milk thistle appeared to help patients tolerate higher doses of chemotherapy. Sixty-one percent of the children receiving milk thistle needed dose reductions, compared with 72 percent of the children receiving placebo, but this difference is not significant, the researchers noted.

Related lab experiments showed the herb did not lessen the effectiveness of the chemotherapy drugs, and Kelly thinks milk thistle might reduce liver inflammation for patients with other cancers who are taking other types of chemotherapy as well. Further research is needed, she said, to determine the appropriate dose and duration of milk thistle therapy.

Her team also hopes to evaluate the herb's ability to prevent chemo-induced liver inflammation.

Still, some experts remain unconvinced about the herb's value in cancer treatment. Dr. Julio C. Barredo, director of pediatric hematology-oncology at the University of Miami Miller School of Medicine, said that the study's small size, the low doses of milk thistle used and the short time frame of the study make the findings inconclusive.

Also, there was no difference in the delay of treatment in either group, he said.

"Improvement in one liver enzyme did not lead to patients who received the drug being delayed less than patients who received placebo in getting their chemotherapy," Barredo said.

"I don't think that you could recommend that people go and take this supplement when they are taking chemotherapy from the results of this study," Barredo said. "Maybe a larger study, using a higher dose is warranted."

Liver inflammation from chemotherapy usually abates when treatment stops or doses get reduced, Barredo added.